CVE-2017-9469 in irssi
Summary
by MITRE
In Irssi before 1.0.3, when receiving certain incorrectly quoted DCC files, it tries to find the terminating quote one byte before the allocated memory. Thus, remote attackers might be able to cause a crash.
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Analysis
by VulDB Data Team • 12/26/2020
The vulnerability identified as CVE-2017-9469 represents a critical memory corruption flaw in Irssi version 1.0.2 and earlier, affecting the popular text-based chat client used extensively in IRC networks. This issue stems from improper handling of DCC (Direct Client-to-Client) file transfers, which are commonly used for sharing files between IRC participants. The flaw manifests when Irssi receives DCC file transfers with incorrectly quoted parameters, creating a scenario where the application attempts to access memory locations beyond the allocated buffer boundaries.
The technical implementation of this vulnerability involves a classic buffer underflow condition where the application's string parsing logic fails to properly validate input boundaries before attempting to locate terminating quote characters. When processing DCC file transfer data, Irssi allocates memory for the file name but subsequently attempts to search for a closing quote character at an offset that extends beyond the allocated memory region. This memory access violation occurs because the software does not properly account for the actual length of the quoted string or validate that the search operation remains within allocated bounds, creating a predictable memory corruption scenario.
From an operational perspective, this vulnerability presents a significant risk to IRC network participants as it allows remote attackers to trigger a denial of service condition through carefully crafted malicious DCC file transfers. The crash occurs during the processing of malformed input data, effectively allowing an attacker to disrupt service for legitimate users without requiring authentication or privileged access. The vulnerability's impact extends beyond simple service disruption as it could potentially be exploited in more sophisticated attacks where the crash might be leveraged as part of a broader exploitation chain, particularly in environments where Irssi is used for critical communications.
The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions in software applications, and represents a specific manifestation of improper input validation that can lead to memory corruption. From an attack framework perspective, this issue maps to the attack technique of remote code execution through memory corruption, though in this specific case it manifests as a denial of service rather than arbitrary code execution. The vulnerability's exploitation requires minimal privileges and can be executed through standard IRC client interactions, making it particularly dangerous in public or untrusted network environments where users might receive unsolicited DCC file transfers.
Mitigation strategies for this vulnerability center on immediate software updates to Irssi version 1.0.3 or later, which contain the necessary patches to properly validate input boundaries during DCC file transfer processing. Network administrators should implement strict firewall rules that restrict DCC file transfers or implement proxy solutions that sanitize IRC traffic before it reaches client applications. Additionally, users should be educated about the risks of accepting DCC file transfers from untrusted sources, and organizations should consider implementing intrusion detection systems that can identify and block suspicious DCC transfer patterns. The patch for this vulnerability demonstrates proper bounds checking implementation and memory allocation validation that prevents the underflow condition from occurring during string parsing operations.